Variable L0 Guidance Strategy: Enlarged Operational Envelope and Path-Following

TL;DR

This paper introduces a variable look-ahead guidance strategy for UAVs that enlarges the operational envelope, enabling smoother, more efficient path-following by adapting to tracking errors and reducing control effort.

Contribution

It proposes a novel exponentially varying look-ahead parameter that significantly enlarges the unsaturated operational region compared to fixed look-ahead guidance.

Findings

Operational envelope increased by over 70% with variable L0

Smoother trajectories and earlier saturation recovery

Reduced control effort during path-following

Abstract

This paper presents a geometric and theoretical study of an exponentially varying look-ahead parameter for UAV path-following guidance. Conventional guidance laws with a fixed look-ahead distance often drive the vehicle into turn-rate saturation when the heading or cross-track error is large, leading to constrained maneuvers and higher control effort. The proposed variable L0 strategy reshapes the look-ahead profile so that the guidance command adapts to the evolving tracking error geometry. A detailed investigation shows that this adaptation significantly enlarges the region in which the commanded turn rate remains unsaturated, allowing the vehicle to operate smoothly over a broader range of error conditions. For representative settings, the unsaturated operational envelope increases by more than 70% relative to the constant L0 formulation. These geometric insights translate to smoother trajectories, earlier recovery from saturation, and reduced control demand. Simulation studies on straight-line and elliptical paths demonstrate the merits of the variable look-ahead strategy, highlighting its control-efficient and reliable path-following performance.